Optimized system for recovering waste heat

ABSTRACT

A waste heat recovery system includes at least two integrated rankine cycle systems coupled to at least two separate heat sources having different temperatures. The first rankine cycle system is coupled to a first heat source and configured to circulate a first working fluid. The second rankine cycle system is coupled to at least one second heat source and configured to circulate a second working fluid. The first and second working fluid are circulatable in heat exchange relationship through a cascading heat exchange unit for condensation of the first working fluid in the first rankine cycle system and evaporation of the second working fluid in the second rankine cycle system. At least one bypass unit is configured to divert at least a portion of the first working fluid to bypass the first evaporator, the first expander, the cascaded heat exchange unit, or combinations thereof; at least a portion of the second working fluid to bypass the second expander, the cascaded heat exchange unit, or combinations thereof.

BACKGROUND

The embodiments disclosed herein relate generally to the field of power generation and, more particularly, to an optimized system for recovering waste heat from a plurality of heat sources having different temperatures for generation of electricity.

Enormous amounts of waste heat are generated by a wide variety of industrial and commercial processes and operations. Example sources of waste heat include heat from space heating assemblies, steam boilers, engines, and cooling systems. When waste heat is low grade, such as waste heat having a temperature of heat below 400 degrees Fahrenheit, for example, conventional heat recovery systems do not operate with sufficient efficiency to make recovery of energy cost-effective. The net result is that vast quantities of waste heat are simply dumped into the surroundings.

Combustion engines are also used to generate electricity using fuels such as gasoline, natural gas, biogas, plant oil, and diesel fuel. However, atmospheric emissions such as nitrogen oxides and particulates may be emitted.

In one conventional method to generate electricity from waste heat, a two-cycle system is used in heat recovery applications with waste heat sources of different temperature levels. In such two-cycle configurations, the hot heat source heats a high-boiling point liquid in a top loop, and the cold heat source heats a low-boiling point liquid in a separate bottom loop. Since the two-cycle systems are more complex and require more components, the overall cost of the two-cycle system is significantly higher.

In another conventional system provided to generate electricity from waste heat, a cascaded organic rankine cycle system for utilization of waste heat includes a pair of organic rankine cycle systems. The cycles are combined, and the respective organic working fluids are chosen such that the organic working fluid of the first organic rankine cycle is condensed at a condensation temperature that is above the boiling point of the organic working fluid of the second organic cycle. A single common heat exchanger is used for both the condenser of the first organic rankine cycle system and the evaporator of the second organic rankine cycle. However, performance of such a system may be reduced under different operating conditions. In other words, performance of such a system may be reduced during partial load and varying ambient conditions.

It is desirable to have an optimized system that effectively recovers waste heat over a wide temperature range from multiple low-grade heat sources at different operating conditions.

BRIEF DESCRIPTION

In accordance with one exemplary embodiment disclosed herein, a waste heat recovery system including at least two integrated rankine cycle systems is provided. The system includes a heat generation system comprising at least two separate heat sources having different temperatures. A first rankine cycle system is coupled to a first heat source among the at least two separate heat sources and configured to circulate a first working fluid. The first rankine system is configured to remove heat from the first heat source. A second rankine cycle system is coupled to at least one second heat source among the at least two separate heat sources and configured to circulate a second working fluid. The at least one second heat source includes a lower temperature heat source than the first heat source. The second rankine cycle system is configured to remove heat from the at least one second heat source. The first and second working fluids are circulatable in a heat exchange relationship through a cascaded heat exchange unit for condensation of the first working fluid in the first rankine cycle system and evaporation of the second working fluid in the second rankine cycle system. At least one bypass unit is configured to divert at least a portion of the first working fluid to bypass the first evaporator, the first expander, the cascaded heat exchange unit, or combinations thereof; at least a portion of the second working fluid to bypass the second expander, the cascaded heat exchange unit, or combinations thereof.

In accordance with one exemplary embodiment disclosed herein, a waste heat recovery system including at least two integrated organic rankine cycle systems is provided. The system includes a combustion engine having an engine exhaust unit; and at least another heat source selected from a group comprising an oil heat exchanger, engine jacket, water jacket heat exchanger, lower temperature intercooler, higher temperature intercooler, or combinations thereof. A first organic rankine cycle system is coupled to the engine exhaust unit and configured to circulate a first organic working fluid. A second organic rankine cycle system is coupled to at least one other heat source selected from the group comprising the oil heat exchanger, engine jacket, water jacket heat exchanger, lower temperature intercooler, higher temperature intercooler, or combinations thereof, and configured to circulate a second organic working fluid. The one heat source includes a lower temperature heat source than at least one other heat source. The second organic rankine cycle system is configured to remove heat from the at least one other heat source. The first and second organic working fluids are circulatable in heat exchange relationship through a cascaded heat exchange unit for condensation of the first organic working fluid in the first organic rankine cycle system and evaporation of the second organic working fluid in the second organic rankine cycle system. At least one bypass unit is configured to divert at least a portion of the first working fluid to bypass the first evaporator, the first expander, the cascaded heat exchange unit, or combinations thereof; at least a portion of the second working fluid to bypass the second expander, the cascaded heat exchange unit, or combinations thereof.

DRAWINGS

These and other features, aspects, and advantages of the present invention will become better understood when the following detailed description is read with reference to the accompanying drawings in which like characters represent like parts throughout the drawings, wherein:

FIG. 1 is a diagrammatical representation of waste heat recovery system having two integrated organic rankine cycle systems with a bypass arrangement in a thermal oil loop in accordance with an exemplary embodiment disclosed herein;

FIG. 2 is a diagrammatical representation of waste heat recovery system having two integrated organic rankine cycle systems with a bypass arrangement in a top loop in accordance with an exemplary embodiment disclosed herein;

FIG. 3 is a diagrammatical representation of waste heat recovery system having two integrated organic rankine cycle systems with a bypass arrangement in a top loop in accordance with an exemplary embodiment disclosed herein;

FIG. 4 is a diagrammatical representation of waste heat recovery system having two integrated organic rankine cycle systems with a bypass arrangement for flow of exhaust gas in accordance with an exemplary embodiment disclosed herein;

FIG. 5 is a diagrammatical representation of waste heat recovery system having two integrated organic rankine cycle systems with a bypass arrangement in a thermal oil loop in accordance with an exemplary embodiment disclosed herein;

FIG. 6 is a diagrammatical representation of waste heat recovery system having two integrated organic rankine cycle systems with a bypass arrangement in a top loop in accordance with an exemplary embodiment disclosed herein;

FIG. 7 is a diagrammatical representation of waste heat recovery system having two integrated organic rankine cycle systems with a bypass arrangement in a bottom loop in accordance with an exemplary embodiment disclosed herein;

FIG. 8 is a diagrammatical representation of waste heat recovery system having two integrated organic rankine cycle systems with a bypass arrangement in a bottom loop in accordance with an exemplary embodiment disclosed herein;

FIG. 9 is a diagrammatical representation of waste heat recovery system having two integrated organic rankine cycle systems with a bypass arrangement in a bottom loop in accordance with an exemplary embodiment disclosed herein; and

FIG. 10 is a diagrammatical representation of waste heat recovery system having two integrated organic rankine cycle systems with a bypass arrangement in a water loop in accordance with an exemplary embodiment disclosed herein.

DETAILED DESCRIPTION

As discussed in detail below, embodiments of the present invention provide a waste heat recovery system having at least two integrated rankine cycle systems coupled to at least two separate heat sources respectively having different temperatures. The first rankine cycle system is coupled to a first heat source and configured to circulate a first working fluid. The second rankine cycle system is coupled to at least one second heat source and configured to circulate a second working fluid. The second heat source includes a lower temperature heat source than the first heat source. The waste heat recovery system also includes a cascaded heat exchange unit. The first and second working fluids are circulated in heat exchange relationship for condensation of the first working fluid in the first rankine cycle system and evaporation of the second working fluid in the second rankine cycle system. At least one bypass unit is configured to divert at least a portion of the first working fluid to bypass the first evaporator, the first expander, or combinations thereof; at least a portion of the second working fluid to bypass the second expander, the cascaded heat exchange unit, or combinations thereof. Various bypasses in the exemplary waste heat recovery system allow the optimized operation of the organic rankine cycle system under different operating conditions. These additional degrees of freedom enable high performance at part load and varying ambient conditions without exceeding component limits, such as maximum pressures, temperatures, or the like. Although the waste heat recovery system in the exemplary embodiments of FIGS. 1-10 is described with reference to combustion engines, the system is also applicable to other heat generation systems such as gas turbines, geothermal, solar, industrial and residential heat sources, or the like.

Referring to FIG. 1, a waste heat recovery system 10 is illustrated in accordance with an exemplary embodiment of the present invention. The illustrated waste heat recovery system 10 includes a first organic rankine cycle system 12 (top cycle) and a second organic rankine cycle system 14 (bottom cycle). A first organic working fluid is circulated through the first organic rankine cycle system 12. The first organic working fluid may include cyclohexane, cyclopentane, thiophene, ketones, aromatics, or combinations thereof. In the illustrated embodiment, the first organic rankine cycle system 12 includes the evaporator 16 coupled to a first heat source 18, i.e. the exhaust unit of the engine, via a thermal oil heat exchanger 20. In the illustrated embodiment, the thermal oil heat exchanger 20 is a shell and tube type heat exchanger. The thermal oil heat exchanger 20 is used to heat thermal oil to a relatively higher temperature using exhaust gas of the engine. The evaporator 16 receives heat from the thermal oil and generates a first organic working fluid vapor. The thermal oil is then pumped back from the evaporator 16 to the thermal oil heat exchanger 20 using a pump 22. In another embodiment, the evaporator 16 may be coupled to the first heat source 18 via an exhaust economizer.

As discussed previously, in conventional systems performance may be reduced under different operating conditions. In other words, performance may be reduced during partial load and varying ambient conditions. In the illustrated embodiment, one bypass unit 24 is configured to divert at least a portion of thermal oil to bypass the evaporator 16. The bypass unit 24 includes a control valve 26 coupled to a bypass path 28. The control valve 26 is configured to control the flow of thermal oil through the bypass path 28. In one embodiment, during partial load conditions or transient conditions, the control valve 26 may be opened so as to divert a portion of heated thermal oil from the thermal oil heat exchanger 20 through the bypass path 28.

The first organic working fluid vapor from the evaporator 16 is passed through a first expander 30 (which in one example includes a radial type expander) to drive a first generator unit 32. In certain other exemplary embodiments, the first expander 30 may be axial type expander, impulse type expander, or high temperature screw type expander. After passing through the first expander 30, the first organic working fluid vapor at a relatively lower pressure and lower temperature is passed through a cascaded heat exchange unit 34. The first organic working fluid vapor is condensed into a liquid, which is then pumped via a pump 36 to the evaporator 16. The cycle may then be repeated.

The cascaded heat exchange unit 34 is used both as a condenser for the first organic rankine cycle system 12 and as evaporator for the second organic rankine cycle system 14. A second organic working fluid is circulated through the second organic rankine cycle system 14. The second organic working fluid may include propane, butane, pentafluoro-propane, pentafluoro-butane, pentafluoro-polyether, oil, or combinations thereof. It should be noted herein that list of first and second organic working fluids are not inclusive and other organic working fluids applicable to organic rankine cycles are also envisaged. In certain other exemplary embodiments, the first or second organic working fluid includes a binary fluid. The binary fluid may include cyclohexane-propane, cyclohexane-butane, cyclopentane-butane, or cyclopentane-pentafluoropropane, for example.

In the illustrated embodiment, the cascaded heat exchange unit 34 is coupled to a plurality of second heat sources such as an intercooler 38, an oil heat exchanger 40, and an engine jacket 42 via a partial evaporator 44. Such second heat sources are also typically coupled to the engine. It should be noted herein that the second heat source includes a lower temperature heat source than the first heat source. The partial evaporator 44 receives heat from a cooling water loop that collects heat from the oil heat exchanger 40, the engine jacket 42, and the intercooler 38 and generates a partially evaporated second organic working fluid two-phase stream. The second organic working fluid stream is passed through the cascaded heat exchange unit 34 for complete evaporation or even superheating of the second organic working fluid. The vaporized second organic working fluid is passed through a second expander 46 to drive a second generator unit 48. After passing through the second expander 46, the second organic working fluid vapor at lower pressure and lower temperature is passed through a condenser 50. The second organic working fluid vapor is condensed into a liquid, which is then pumped via a pump 52 to the partial evaporator 44. The partial evaporator 44 is configured to partially evaporate the liquid being supplied to the cascaded heat exchange unit 34. The fluid in the cooling water loop is pumped via a pump 54 to the oil heat exchanger 40, before being supplied to the engine jacket 42, and the intercooler 38 before it enters the partial evaporator 44. The cycle may then be repeated.

It should be noted that in other exemplary embodiments, first and second heat sources may include other multiple low-grade heat sources such as gas turbines with intercoolers. The cascaded heat exchange unit 24 receives heat from the first organic working fluid and generates a second organic working fluid vapor. The second organic working fluid vapor is passed through a second expander 34 (which in one example includes a screw type compressor) to drive a second generator unit 36. In certain other exemplary embodiments, the second expander 34 may be a radial type expander, an axial type expander, or an impulse type expander. In certain other exemplary embodiments, the first expander 20 and the second expander 34 are coupled to a single generator unit.

The cascaded organic rankine cycle system facilitates heat recovery over a temperature range that is too large for a single organic rankine cycle system to accommodate efficiently. The illustrated layout of the second heat sources facilitates effective heat removal from the plurality of lower temperature engine heat sources. This increases the effectiveness of the cooling systems and provides effective conversion of waste heat into electricity.

In another exemplary embodiment of the present invention, the heat generation system may include a gas turbine system. Steam may be circulated through the top cycle and the second organic working fluid may be circulated through the bottom cycle. Steam is condensed and passed in heat exchange relationship with the second organic working fluid through the cascaded heat exchange unit 34.

Referring to FIG. 2, a waste heat recovery system 10 is illustrated in accordance with an exemplary embodiment of the present invention. The illustrated waste heat recovery system 10 includes the first organic rankine cycle system 12 and the second organic rankine cycle system 14. In the illustrated embodiment, the first organic rankine cycle system 12 includes the evaporator 16 coupled to the first heat source 18, for example an exhaust unit of a heat generation system 56 (for example, an engine). The evaporator 16 receives heat from the exhaust gas generated from the first heat source 18 and generates a first organic working fluid vapor. The first organic working fluid vapor is passed through the first expander 30 to drive the first generator unit 32. After passing through the first expander 20, the first organic working fluid vapor at a relatively lower pressure and lower temperature is passed through the cascaded heat exchange unit 34. The first organic working fluid vapor is condensed into a liquid, which is then pumped via the pump 36 to the evaporator 16.

In the illustrated embodiment, one bypass unit 58 is configured to divert at least a portion of the condensed first organic working fluid from the pump 36 to bypass the evaporator 16. The bypass unit 58 includes a control valve 60 coupled to a bypass path 62. The control valve 60 is configured to control the flow of the first organic working fluid through the bypass path 62. In one embodiment, during partial load conditions or transient conditions, the control valve 60 may be opened so as to divert a portion of the condensed first organic working fluid from the pump 36 through the bypass path 62.

In the illustrated embodiment, the cascaded heat exchange unit 34 may be coupled to any one or more of a plurality of second heat sources such as the intercooler 38, the oil heat exchanger 40, and a cooling water jacket heat exchanger 64. Such second heat sources are also typically coupled to the engine. After passing through the second expander 46, the second organic working fluid vapor at lower pressure and lower temperature is passed through the condenser 50. The second organic working fluid vapor is condensed into a liquid, which is then pumped via the pump 52 to the second heat sources. In the illustrated embodiment, the second organic working fluid is pumped sequentially via the intercooler 38, the oil heat exchanger 40, and the cooling water jacket heat exchanger 64.

Referring to FIG. 3, a waste heat recovery system 10 is illustrated in accordance with an exemplary embodiment of the present invention. This embodiment is similar to the embodiment discussed with reference to FIG. 2. In the illustrated embodiment, one bypass unit 59 is configured to divert at least a portion of the expanded first organic working fluid from the first expander 30 to bypass the cascaded heat exchange unit 34. The bypass unit 59 includes a control valve 61 coupled to a bypass path 63. The control valve 61 is configured to control the flow of the first organic working fluid through the bypass path 63. In one embodiment, during partial load conditions or transient conditions, the control valve 61 may be opened so as to divert a portion of the expanded first organic working fluid from the first expander 30 through the bypass path 63.

Referring to FIG. 4, a waste heat recovery system 10 is illustrated in accordance with an exemplary embodiment of the present invention. This embodiment is similar to the embodiment illustrated in FIG. 1. In the illustrated embodiment, the first organic rankine cycle system 12 includes the evaporator 16 coupled to the first heat source (not shown) via the thermal oil heat exchanger 20. The thermal oil heat exchanger 20 is used to heat thermal oil to a relatively higher temperature using exhaust gas of the engine. In the illustrated embodiment, one bypass unit 65 is configured to divert at least a portion of the exhaust gas from the first heat source to bypass the thermal oil heat exchanger 20. The bypass unit 65 includes a control valve 66 coupled to a bypass path 68. The control valve 66 is configured to control the flow of exhaust gas through the bypass path 68. In one embodiment, during partial load conditions or transient conditions, the control valve 66 may be opened so as to divert a portion of the exhaust gas from the first heat source through the bypass path 68.

Referring to FIG. 5, a waste heat recovery system 10 is illustrated in accordance with an exemplary embodiment of the present invention. In the illustrated embodiment, the first organic rankine cycle system 12 includes the evaporator 16 coupled to the first heat source, i.e. the exhaust unit of the engine, via the thermal oil heat exchanger 20 and an exhaust economizer 70. The thermal oil is then pumped back from the evaporator 16 to the thermal oil heat exchanger 42 using the pump 22. In the illustrated embodiment, the condensed liquid (i.e. first organic working fluid) from the cascaded heat exchange unit 34 is pumped via the pump 36 to the exhaust economizer 70. The condensed liquid is heated prior to being supplied to the evaporator 16.

In the illustrated embodiment, one bypass unit 72 is configured to divert at least a portion of the thermal oil from the pump 22 to bypass the thermal oil heat exchanger 20. The bypass unit 72 includes a control valve 74 coupled to a bypass path 76. The control valve 74 is configured to control the flow of thermal oil through the bypass path 76. In one embodiment, during partial load conditions or transient conditions, the control valve 74 may be opened so as to divert a portion of the thermal oil from the pump 22 through the bypass path 76.

In the illustrated embodiment, the cascaded heat exchange unit 34 is coupled to a plurality of second heat sources such as the lower temperature intercooler 38, the oil heat exchanger 40, the water jacket heat exchanger 64, and a higher temperature intercooler 78. The heat sources disclosed herein may be coupled in series or parallel. The relative positions of the heat sources may also be varied depending upon the requirement.

Referring to FIG. 6, a waste heat recovery system 10 is illustrated in accordance with an exemplary embodiment of the present invention. The illustrated waste heat recovery system 10 includes the first organic rankine cycle system 12 and the second organic rankine cycle system 14. In the illustrated embodiment, the first organic rankine cycle system 12 includes the evaporator 16 coupled to the first heat source 18. The evaporator 16 receives heat from the exhaust gas generated from the first heat source 18 and generates a first organic working fluid vapor. The first organic working fluid vapor is passed through the first expander 30 to drive the first generator unit 32. After passing through the first expander 20, the first organic working fluid vapor at a relatively lower pressure and lower temperature is passed through the cascaded heat exchange unit 34. The first organic working fluid vapor is condensed into a liquid, which is then pumped via the pump 36 to the evaporator 16.

In the illustrated embodiment, one bypass unit 80 is configured to divert at least a portion of the first organic working fluid vapor from the evaporator 16 to bypass the first expander 20. The bypass unit 80 includes a three-way valve 82 and a pressure reduction valve 84 coupled to a bypass path 86. The three-way valve 82 is configured to control the flow of first organic working fluid through the bypass path 86. In one embodiment, during partial load conditions or transient conditions, the three-way valve 82 may be opened so as to divert a portion of the first organic working fluid vapor from the evaporator 16 through the bypass path 86. The pressure reduction valve 84 is configured to control the pressure of the first organic working fluid vapor flowing through the bypass path 86.

Referring to FIG. 7, a waste heat recovery system 10 is illustrated in accordance with another exemplary embodiment of the present invention. In the illustrated embodiment, the cascaded heat exchange unit 34 is coupled to a plurality of second heat sources such as the intercooler 38, the oil heat exchanger 40, and the water jacket heat exchanger 64. The second heat sources are used to preheat or partially vaporize the second organic working fluid entering the cascading heat exchange unit 34. The cascaded heat exchange unit 34 receives heat from the first organic working fluid and generates a second organic working fluid vapor. The second organic working fluid vapor is fed to the second expander 46 to drive the second generator unit 48. After passing the second organic working fluid through the second expander 46, the second organic working fluid vapor at lower pressure and lower temperature is passed through the condenser 50. The second organic working fluid vapor is condensed into a liquid, which is then pumped via the pump 52 to the lower temperature intercooler 38.

In the illustrated embodiment, one bypass unit 88 is configured to divert at least a portion of the second organic working fluid vapor from the cascaded heat exchange unit 34 to bypass the second expander 46. The bypass unit 88 includes a three-way valve 90 and a pressure reduction valve 92 coupled to a bypass path 94. The three-way valve 90 is configured to control the flow of second organic working fluid through the bypass path 94. In one embodiment, during partial load conditions or transient conditions, the three-way valve 90 may be opened so as to divert a portion of the second organic working fluid vapor from the cascaded heat exchange unit 34 through the bypass path 94. The pressure reduction valve 92 is configured to control the pressure of the second organic working fluid vapor flowing through the bypass path 94.

Referring to FIG. 8, a waste heat recovery system 10 is illustrated in accordance with another exemplary embodiment of the present invention. In the illustrated embodiment, the cascaded heat exchange unit 34 is coupled to a plurality of second heat sources such as the intercooler 38, the oil heat exchanger 40, and the engine jacket 42 via the partial evaporator 44. The partial evaporator 44 receives heat from a cooling water loop that collects heat from the oil heat exchanger 40, the engine jacket 42, and the intercooler 38 and generates a partially evaporated second organic working fluid two-phase stream. The second organic working fluid stream is passed through the cascaded heat exchange unit 34 for complete evaporation or even superheating of the second organic working fluid. The vaporized second organic working fluid is passed through the second expander 46 to drive the second generator unit 48. After passing through the second expander 46, the second organic working fluid vapor at lower pressure and lower temperature is passed through the condenser 50. The second organic working fluid vapor is condensed into a liquid, which is then pumped via the pump 52 to the partial evaporator 44.

In the illustrated embodiment, one bypass unit 96 is configured to divert at least a portion of the second organic working fluid from the partial evaporator 44 to bypass the cascaded heat exchange unit 34. The bypass unit 96 includes a control valve 98 coupled to a bypass path 100. The control valve 98 is configured to control the flow of second organic working fluid through the bypass path 100. In one embodiment, during partial load conditions or transient conditions, the control valve 98 may be opened so as to divert a portion of the second organic working fluid from the partial evaporator 44 through the bypass path 100.

Referring to FIG. 9, a waste heat recovery system 10 is illustrated in accordance with another exemplary embodiment of the present invention. This embodiment is similar to the embodiment illustrated in FIG. 8. In the illustrated embodiment, one bypass unit 102 is configured to divert at least a portion of the condensed second organic working fluid from the pump 52 to bypass the partial evaporator 44. The bypass unit 102 includes a control valve 104 coupled to a bypass path 106. The control valve 104 is configured to control the flow of the condensed second organic working fluid through the bypass path 106. In one embodiment, during partial load conditions or transient conditions, the control valve 104 may be opened so as to divert a portion of the condensed second organic working fluid from the pump 52 through the bypass path 106.

Referring to FIG. 10, a waste heat recovery system 10 is illustrated in accordance with another exemplary embodiment of the present invention. This embodiment is also similar to the embodiment illustrated in FIG. 8. In the illustrated embodiment, one bypass unit 108 is configured to divert at least a portion of water (mixture of water and glycol) from the intercooler 38 to bypass the partial evaporator 44. The bypass unit 108 includes a control valve 110 coupled to a bypass path 112. The control valve 110 is configured to control the flow of water through the bypass path 112. In one embodiment, during partial load conditions or transient conditions, the control valve 110 may be opened so as to divert a portion of water from the intercooler 38 through the bypass path 112.

It should be noted herein with the reference to embodiments discussed above, a bypass unit may include a three-way valve (for example, as discussed in embodiments of FIGS. 6 and 7), a control valve (for example, as discussed in embodiments of FIGS. 1-5, and FIGS. 8-10), a pressure reduction valve (for example, as discussed in embodiments of FIGS. 6 and 7), or combinations thereof coupled to a bypass path. In certain embodiments, a three-way valve may be used as a “splitter” and may be disposed upstream of a component to be bypassed. In some other embodiments, a three-way valve may be used as a “mixer” and may be disposed downstream of a component to be bypassed. In a particular embodiment, a control valve may also be a three-way valve.

With reference to the embodiments discussed above, although one evaporator 16, one cascaded heat exchange unit 34, and one partial evaporator 44 is shown, in some embodiments, more than one evaporator 16, cascaded heat exchange unit 34, partial evaporator 44 may be used. In such embodiments, an exemplary bypass unit may be provided across the more than one evaporator 16, cascaded heat exchange unit 34, and partial evaporator 44.

The various bypass arrangements discussed herein with reference to FIGS. 1-9 enhances thermodynamic efficiency and effective heat recovery of the overall system. It should be noted herein that in other embodiments of the exemplary recuperated waste heat recovery system, the number of second heat sources such as intercoolers, oil heat exchangers, jacket heat exchangers, evaporators and their relative positions and their relative positions in the second organic rankine cycle system may be varied depending the application. All such permutations and combinations are envisaged. Various such permutations and combinations discussed in U.S. patent application No. 11/770,895 filed on Jun. 29, 2007 is incorporated herein by reference.

While only certain features of the invention have been illustrated and described herein, many modifications and changes will occur to those skilled in the art. It is, therefore, to be understood that the appended claims are intended to cover all such modifications and changes as fall within the true spirit of the invention. 

1. A waste heat recovery system including at least two integrated rankine cycle systems, the recovery system comprising: a heat generation system comprising at least two separate heat sources having different temperatures; a first rankine cycle system comprising a first evaporator and a first expander, wherein the first rankine cycle system is coupled to a first heat source among the at least two separate heat sources and configured to circulate a first working fluid; wherein the first rankine system is configured to remove heat from the first heat source; a second rankine cycle system comprising a second evaporator and a second expander; wherein the second rankine cycle system is coupled to at least one second heat source among the at least two separate heat sources and configured to circulate a second working fluid, the at least one second heat source comprising a lower temperature heat source than the first heat source, wherein the second rankine cycle system is configured to remove heat from the at least one second heat source; a cascaded heat exchange unit, wherein the first and second working fluids are circulatable in heat exchange relationship through the cascaded heat exchange unit for condensation of the first working fluid in the first rankine cycle system and evaporation of the second working fluid in the second rankine cycle system; and at least one bypass unit configured to divert at least a portion of the first working fluid to bypass the first evaporator, the first expander, the cascaded heat exchange unit, or combinations thereof; at least a portion of the second working fluid to bypass the second expander, the cascaded heat exchange unit, or combinations thereof.
 2. The recovery system of claim 1, wherein the first evaporator is coupled to the first heat source, and wherein the first heat source comprises an engine exhaust unit.
 3. The recovery system of claim 2, wherein the first evaporator is coupled to the engine exhaust unit via a thermal oil heat exchanger, exhaust economizer, or combinations thereof.
 4. The recovery system of claim 3, further comprising one bypass unit configured to divert at least a portion of thermal oil to bypass the first evaporator; wherein the one bypass unit comprises a control valve coupled to a bypass path.
 5. The recovery system of claim 3, further comprising one bypass unit configured to divert at least a portion of thermal oil to bypass the thermal oil heat exchanger; wherein the one bypass unit comprises a control valve coupled to a bypass path.
 6. The recovery system of claim 2, further comprising one bypass unit configured to divert at least a portion of engine exhaust gas to bypass the thermal oil heat exchanger; wherein the one bypass unit comprises a control valve coupled to a bypass path.
 7. The recovery system of claim 1, wherein the second rankine cycle system comprises a condenser coupled to the at least one second heat source selected from a group comprising an oil heat exchanger, an engine jacket, a water jacket heat exchanger, a lower temperature intercooler, a higher temperature intercooler, or combinations thereof.
 8. The recovery system of claim 7, further comprising a partial evaporator; wherein the condenser is coupled to the oil heat exchanger, the engine jacket, the water jacket heat exchanger, the engine jacket, the lower temperature intercooler, the higher temperature intercooler, or combinations thereof through the partial evaporator configured to partially evaporate the second working fluid before entering the cascaded heat exchange unit.
 9. The recovery system of claim 8, further comprising one bypass unit configured to divert at least a portion of water to bypass the partial evaporator; wherein the one bypass unit comprises a control valve coupled to a bypass path.
 10. The recovery system of claim 8, further comprising one bypass unit configured to divert at least a portion of the second working fluid to bypass the partial evaporator, wherein the one bypass unit comprises a control valve coupled to a bypass path.
 11. The recovery system of claim 1, wherein the at least one bypass unit comprises a control valve, a three-way valve, pressure reduction valve, or combinations thereof coupled to a bypass path.
 12. A waste heat recovery system including at least two integrated organic rankine cycle systems, the recovery system comprising: a combustion engine comprising one heat source having an engine exhaust unit; and at least one other heat source selected from a group comprising an oil heat exchanger, an engine jacket, a water jacket heat exchanger, a lower temperature intercooler, a higher temperature intercooler, or combinations thereof; a first organic rankine cycle system comprising a first evaporator and a first expander, wherein the first organic rankine cycle system is coupled to the engine exhaust unit and configured to circulate a first organic working fluid; wherein the first organic rankine system is configured to remove heat from the engine exhaust unit; a second organic rankine cycle system comprising a second evaporator and a second expander; wherein the second organic rankine cycle system is coupled to the at least one other heat source selected from the group comprising the oil heat exchanger, the engine jacket, the water jacket heat exchanger, the lower temperature intercooler, the higher temperature intercooler, or combinations thereof; and configured to circulate a second organic working fluid, the one heat source comprising a higher temperature heat source than the at least one other heat source, wherein the second organic rankine cycle system is configured to remove heat from the at least one other heat source; and a cascaded heat exchange unit, wherein the first and second organic working fluids are circulatable in heat exchange relationship through the cascaded heat exchange unit for condensation of the first organic working fluid in the first organic rankine cycle system and evaporation of the second organic working fluid in the second organic rankine cycle system; at least one bypass unit configured to divert at least a portion of the first working fluid to bypass the first evaporator, the first expander, the cascaded heat exchange unit, or combinations thereof; at least a portion of the second working fluid to bypass the second expander, the cascaded heat exchange unit, or combinations thereof.
 13. The recovery system of claim 12, wherein the first evaporator is coupled to the engine exhaust unit via a thermal oil heat exchanger, exhaust economizer, or combinations thereof.
 14. The recovery system of claim 13, further comprising one bypass unit configured to divert at least a portion of thermal oil to bypass the first evaporator; wherein the one bypass unit comprises a control valve coupled to a bypass path.
 15. The recovery system of claim 13, further comprising one bypass unit configured to divert at least a portion of thermal oil to bypass the thermal oil heat exchanger; wherein the one bypass unit comprises a control valve coupled to a bypass path.
 16. The recovery system of claim 12, further comprising one bypass unit configured to divert at least a portion of engine exhaust gas to bypass the thermal oil heat exchanger; wherein the one bypass unit comprises a control valve coupled to a bypass path.
 17. The recovery system of claim 12, wherein the second rankine cycle system comprises a condenser coupled to the at least one other heat source selected from a group comprising an oil heat exchanger, an engine jacket, a water jacket heat exchanger, a lower temperature intercooler, a higher temperature intercooler, or combinations thereof.
 18. The recovery system of claim 17, further comprising a partial evaporator; wherein the condenser is coupled to the oil heat exchanger, the engine jacket, the water jacket heat exchanger, the engine jacket, the lower temperature intercooler, the higher temperature intercooler, or combinations thereof through the partial evaporator configured to partially evaporate the second working fluid before entering the cascaded heat exchange unit.
 19. The recovery system of claim 18, further comprising one bypass unit configured to divert at least a portion of water to bypass the partial evaporator; wherein the one bypass unit comprises a control valve coupled to a bypass path.
 20. The recovery system of claim 18, further comprising one bypass unit configured to divert at least a portion of the second working fluid to bypass the partial evaporator, wherein the one bypass unit comprises a control valve coupled to a bypass path.
 21. The recovery system of claim 12, wherein the at least one bypass unit comprises a control valve, a three-way valve, pressure reduction valve, or combinations thereof coupled to a bypass path.
 22. A waste heat recovery system including at least two integrated rankine cycle systems, the recovery system comprising: a heat generation system comprising at least two separate heat sources having different temperatures; a first rankine cycle system comprising a first evaporator and a first expander, wherein the first rankine cycle system is coupled to a first heat source among the at least two separate heat sources and configured to circulate a first working fluid; wherein the first rankine system is configured to remove heat from the first heat source; a second rankine cycle system comprising a second evaporator and a second expander; wherein the second rankine cycle system is coupled to at least one second heat source among the at least two separate heat sources and configured to circulate a second working fluid, the at least one second heat source comprising a lower temperature heat source than the first heat source, wherein the second rankine cycle system is configured to remove heat from the at least one second heat source; a cascaded heat exchange unit, wherein the first and second working fluids are circulatable in heat exchange relationship through the cascaded heat exchange unit for condensation of the first working fluid in the first rankine cycle system and evaporation of the second working fluid in the second rankine cycle system; wherein the second rankine cycle is configured to preheat and/or partially evaporate the second working fluid before entering the cascaded heat exchange unit and at least one bypass unit configured to divert at least a portion of the first working fluid to bypass the first evaporator, the first expander, the cascaded heat exchange unit, or combinations thereof; at least a portion of the second working fluid to bypass the second expander, the cascaded heat exchange unit, or combinations thereof.
 23. The recovery system of claim 22, wherein the second rankine cycle system comprises a condenser coupled to the at least one second heat source selected from a group comprising an oil heat exchanger, an engine jacket, a water jacket heat exchanger, a lower temperature intercooler, a higher temperature intercooler, or combinations thereof.
 24. The recovery system of claim 23, further comprising a partial evaporator; wherein the condenser is coupled to the oil heat exchanger, the engine jacket, the water jacket heat exchanger, the engine jacket, the lower temperature intercooler, the higher temperature intercooler, or combinations thereof through the partial evaporator configured to partially evaporate the second working fluid before entering the cascaded heat exchange unit.
 25. The recovery system of claim 24, further comprising one bypass unit configured to divert at least a portion of water to bypass the partial evaporator; wherein the one bypass unit comprises a control valve coupled to a bypass path.
 26. The recovery system of claim 24, further comprising one bypass unit configured to divert at least a portion of the second working fluid to bypass the partial evaporator, wherein the one bypass unit comprises a control valve coupled to a bypass path.
 27. The recovery system of claim 22, wherein the at least one bypass unit comprises a control valve, a three-way valve, pressure reduction valve, or combinations thereof coupled to a bypass path. 